This is a note to let you know that I've just added the patch titled
serial: 8250_dw: Fix deadlock in LCR workaround
to the 3.19-stable tree which can be found at:
http://www.kernel.org/git/?p=linux/kernel/git/stable/stable-queue.git;a=summary
The filename of the patch is:
serial-8250_dw-fix-deadlock-in-lcr-workaround.patch
and it can be found in the queue-3.19 subdirectory.
If you, or anyone else, feels it should not be added to the stable tree,
please let <stable@xxxxxxxxxxxxxxx> know about it.
>From 7fd6f640f2dd17dac6ddd6702c378cb0bb9cfa11 Mon Sep 17 00:00:00 2001
From: Peter Hurley <peter@xxxxxxxxxxxxxxxxxx>
Date: Wed, 11 Mar 2015 09:19:16 -0400
Subject: serial: 8250_dw: Fix deadlock in LCR workaround
From: Peter Hurley <peter@xxxxxxxxxxxxxxxxxx>
commit 7fd6f640f2dd17dac6ddd6702c378cb0bb9cfa11 upstream.
Trying to write console output from within the serial console driver
while the port->lock is held causes recursive deadlock:
CPU 0
spin_lock_irqsave(&port->lock)
printk()
console_unlock()
call_console_drivers()
serial8250_console_write()
spin_lock_irqsave(&port->lock)
** DEADLOCK **
The 8250_dw i/o accessors try to write a console error message if the
LCR workaround was unsuccessful. When the port->lock is already held
(eg., when called from serial8250_set_termios()), this deadlocks.
Make the error message a FIXME until a general solution is devised.
Cc: Tim Kryger <tim.kryger@xxxxxxxxx>
Reported-by: Zhang Zhen <zhenzhang.zhang@xxxxxxxxxx>
Signed-off-by: Peter Hurley <peter@xxxxxxxxxxxxxxxxxx>
Signed-off-by: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx>
---
drivers/tty/serial/8250/8250_dw.c | 15 ++++++++++++---
1 file changed, 12 insertions(+), 3 deletions(-)
--- a/drivers/tty/serial/8250/8250_dw.c
+++ b/drivers/tty/serial/8250/8250_dw.c
@@ -111,7 +111,10 @@ static void dw8250_serial_out(struct uar
dw8250_force_idle(p);
writeb(value, p->membase + (UART_LCR << p->regshift));
}
- dev_err(p->dev, "Couldn't set LCR to %d\n", value);
+ /*
+ * FIXME: this deadlocks if port->lock is already held
+ * dev_err(p->dev, "Couldn't set LCR to %d\n", value);
+ */
}
}
@@ -155,7 +158,10 @@ static void dw8250_serial_outq(struct ua
__raw_writeq(value & 0xff,
p->membase + (UART_LCR << p->regshift));
}
- dev_err(p->dev, "Couldn't set LCR to %d\n", value);
+ /*
+ * FIXME: this deadlocks if port->lock is already held
+ * dev_err(p->dev, "Couldn't set LCR to %d\n", value);
+ */
}
}
#endif /* CONFIG_64BIT */
@@ -179,7 +185,10 @@ static void dw8250_serial_out32(struct u
dw8250_force_idle(p);
writel(value, p->membase + (UART_LCR << p->regshift));
}
- dev_err(p->dev, "Couldn't set LCR to %d\n", value);
+ /*
+ * FIXME: this deadlocks if port->lock is already held
+ * dev_err(p->dev, "Couldn't set LCR to %d\n", value);
+ */
}
}
Patches currently in stable-queue which might be from peter@xxxxxxxxxxxxxxxxxx are
queue-3.19/serial-core-fix-iotype-userspace-breakage.patch
queue-3.19/console-fix-console-name-size-mismatch.patch
queue-3.19/serial-8250_dw-fix-deadlock-in-lcr-workaround.patch
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